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Impaired mechanisms of suppression in amblyopia

机译：弱视的抑制机制受损

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Amblyopia is often accompanied by suppression of visual signals from the weaker eye. Physiological studies of amblyopia suggest that intracortical inhibition may play a role in mediating amblyopic suppression. We investigated whether other suppressive phenomena tied to intracortical inhibition are also impaired in amblyopia. Specifically, we measured the magnitude of surround suppression, overlay suppression, and interocular suppression in amblyopes and healthy controls, using well-established psychophysical measures. When a stimulus with surround mask was presented to amblyopesa?? dominant eye (DE), perceived contrast of that stimulus was reduced, and the magnitude of surround suppression was comparable to that of controls. In contrast, surround suppression associated with the amblyopic eye (AE) was significantly stronger in comparison to the DE and to control subjects. In our overlay suppression task, contrast detection thresholds were measured for a Gabor patch embedded in noise relative to when it was presented alone. Elevations in contrast thresholds were significantly lower when the masked Gabor patch was presented to the AE in comparison to the DE, consistent with previous findings. In contrast, overlay suppression measured with amblyopesa?? DE was comparable to that of controls. Finally, we used flash suppression to measure elevations in contrast increment discrimination thresholds for an eye when it was suppressed relative to when it was dominant. In line with previous studies, amblyopes showed a significant imbalance in interocular suppression relative to controls, which was attributed to diminished flash suppression of the DE by the AE. The magnitude of surround suppression and to a weaker extent, interocular suppression was predictive of the severity of amblyopia, as indexed by interocular differences in acuity. Our results are consistent with physiological evidence that amblyopia is associated with heightened GABAergic inhibition and that surround and interocular suppression, but not overlay suppression, are most likely mediated by intracortical inhibition.
机译：弱视通常伴随着来自弱视的视觉信号受到抑制。弱视的生理研究表明，皮层内抑制可能在介导弱视抑制中起作用。我们研究了弱视与其他与皮层内抑制有关的抑制现象是否也受损。具体来说，我们使用完善的心理物理测量方法测量了弱视和健康对照者的周围抑制，重叠抑制和眼内抑制的幅度。什么时候给弱视提供了带有环绕声的刺激？优势眼（DE），该刺激的感知对比度降低，并且环绕抑制的幅度与对照组相当。相反，与DE和对照组相比，弱视眼（AE）引起的周围抑制明显更强。在我们的重叠抑制任务中，相对于单独显示时，测量了嵌入噪声中的Gabor贴片的对比度检测阈值。与DE相比，当将遮罩的Gabor面片呈现给AE时，对比阈值的升高明显更低。相比之下，弱视测量覆盖抑制？ DE与对照组相当。最后，我们使用闪光灯抑制来测量相对于占主导地位的眼睛，当其被抑制时对比度对比判别阈值的升高。与以前的研究一致，弱视显示出相对于对照组的眼内压制不平衡，这归因于AE对DE的闪光抑制作用减弱。环绕声抑制的程度以及在较弱的程度上，眼内抑制可预测弱视的严重程度，这是由眼内视力差异来指示的。我们的结果与生理证据一致，即弱视与增强的GABA能抑制相关，并且周围和眼内抑制而非重叠抑制很可能是由皮质内抑制介导的。

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